Alcoholism, a disease of considerable morbidity, mortality and human suffering worldwide, is first and foremost characterized by excessive alcohol drinking. An integration of behavioral, genetic and molecular tools will be used to test the "Two-Hit hypothesis" that both genetic and environmental factors contribute to excessive alcohol intake. Discovery-based molecular methods will test the expanded hypothesis that genetic differences and alcohol neuroadaptive changes in the expression of several genes are involved in excessive alcohol drinking traits. The first objective of this application is to use the well characterized, genetically selected inbred strains of rats, iP and iNP (preferring and non-preferring respectively), and an environmentally induced paradigm for excessive drinking termed RADE (Repeated Alcohol Deprivation Effect), to complete initial molecular analysis using mRNA differential display (DD) and isolate and identify genes involved in both the genetic propensity and alcohol specific neuroadaptation underlying the excessive drinking phenotype. Of particular focus will be the extended amygdala, posited to be involved in "craving" aspects of alcoholism. Genes cloned in the initial DD screen will be added as additional targets on a custom rat DNA microarray and expression will then be profiled over time and across several brain regions to assess important global changes. The second specific aim is to isolate an amygdala specific gene with the distinct purpose of adapting it for use as a molecular tool to dissect the overall role of this unique brain region. Aim three will include profiling gene expression in brain from a newly developed INIA mouse model that will be created to self-administer alcohol to the extent that will elicit signs of dependence upon withdrawal. DD will again be initially performed followed by custom DNA microarray analysis including the added new mouse DD targets. The fourth aim provides validation of expression using Real-time PCR, Northern and RPA analysis, and in situ hybridization. Where feasible, Western blotting and immunohistochemistry will be used to verify consequent protein level changes relevant to excessive alcohol drinking analysis. All information on the protocol and results of the genetic expression profiling will be freely shared by deposition in the MGI data base (http:/www.informatice.jax.org) as well as a newly created INIA website. Finally, functional characterization of a subset of the identified genes from Aims 1-3 will be completed.